1 /* $OpenBSD: boot.c,v 1.24 2016/10/10 00:34:50 bluhm Exp $ */ 2 /* $NetBSD: boot.c,v 1.5 1997/10/17 11:19:23 ws Exp $ */ 3 4 /* 5 * Copyright (C) 1995, 1997 Wolfgang Solfrank 6 * Copyright (c) 1995 Martin Husemann 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR 18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20 * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT, 21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 #include <sys/param.h> /* DEV_BSIZE powerof2 */ 30 #include <sys/disklabel.h> 31 32 #include <stdlib.h> 33 #include <string.h> 34 #include <ctype.h> 35 #include <stdio.h> 36 #include <unistd.h> 37 38 #include "ext.h" 39 40 int 41 readboot(int dosfs, struct bootblock *boot) 42 { 43 u_char *block = NULL; 44 u_char *fsinfo = NULL; 45 u_char *backup = NULL; 46 int ret = FSOK, secsize = lab.d_secsize, fsinfosz; 47 off_t o; 48 ssize_t n; 49 50 if (secsize < DOSBOOTBLOCKSIZE) { 51 xperror("sector size < DOSBOOTBLOCKSIZE"); 52 goto fail; 53 } 54 if (DOSBOOTBLOCKSIZE != DEV_BSIZE) { 55 xperror("DOSBOOTBLOCKSIZE != DEV_BSIZE"); 56 goto fail; 57 } 58 59 block = malloc(secsize); 60 if (block == NULL) { 61 xperror("could not malloc boot block"); 62 goto fail; 63 } 64 65 if ((o = lseek(dosfs, 0, SEEK_SET)) == -1) { 66 xperror("could not seek boot block"); 67 goto fail; 68 } 69 70 n = read(dosfs, block, secsize); 71 if (n == -1 || n != secsize) { 72 xperror("could not read boot block"); 73 goto fail; 74 } 75 76 if (block[510] != 0x55 || block[511] != 0xaa) { 77 pfatal("Invalid signature in boot block: %02x%02x\n", 78 block[511], block[510]); 79 } 80 81 memset(boot, 0, sizeof *boot); 82 boot->ValidFat = -1; 83 84 /* decode bios parameter block */ 85 boot->BytesPerSec = block[11] + (block[12] << 8); 86 if (boot->BytesPerSec == 0 || boot->BytesPerSec != secsize) { 87 pfatal("Invalid sector size: %u\n", boot->BytesPerSec); 88 goto fail; 89 } 90 boot->SecPerClust = block[13]; 91 if (boot->SecPerClust == 0 || !powerof2(boot->SecPerClust)) { 92 pfatal("Invalid cluster size: %u\n", boot->SecPerClust); 93 goto fail; 94 } 95 boot->ResSectors = block[14] + (block[15] << 8); 96 boot->FATs = block[16]; 97 if (boot->FATs == 0) { 98 pfatal("Invalid number of FATs: %u\n", boot->FATs); 99 goto fail; 100 } 101 boot->RootDirEnts = block[17] + (block[18] << 8); 102 boot->Sectors = block[19] + (block[20] << 8); 103 boot->Media = block[21]; 104 boot->FATsmall = block[22] + (block[23] << 8); 105 boot->SecPerTrack = block[24] + (block[25] << 8); 106 boot->Heads = block[26] + (block[27] << 8); 107 boot->HiddenSecs = block[28] + (block[29] << 8) + (block[30] << 16) + (block[31] << 24); 108 boot->HugeSectors = block[32] + (block[33] << 8) + (block[34] << 16) + (block[35] << 24); 109 110 boot->FATsecs = boot->FATsmall; 111 112 if (!boot->RootDirEnts) { 113 boot->flags |= FAT32; 114 boot->FATsecs = block[36] + (block[37] << 8) 115 + (block[38] << 16) + (block[39] << 24); 116 if (block[40] & 0x80) 117 boot->ValidFat = block[40] & 0x0f; 118 119 /* check version number: */ 120 if (block[42] || block[43]) { 121 /* Correct? XXX */ 122 pfatal("Unknown filesystem version: %x.%x\n", 123 block[43], block[42]); 124 goto fail; 125 } 126 boot->RootCl = block[44] + (block[45] << 8) 127 + (block[46] << 16) + (block[47] << 24); 128 boot->FSInfo = block[48] + (block[49] << 8); 129 boot->Backup = block[50] + (block[51] << 8); 130 131 o = lseek(dosfs, boot->FSInfo * secsize, SEEK_SET); 132 if (o == -1 || o != boot->FSInfo * secsize) { 133 xperror("could not seek fsinfo block"); 134 goto fail; 135 } 136 137 if ((2 * DOSBOOTBLOCKSIZE) < secsize) 138 fsinfosz = secsize; 139 else 140 fsinfosz = 2 * secsize; 141 fsinfo = malloc(fsinfosz); 142 if (fsinfo == NULL) { 143 xperror("could not malloc fsinfo"); 144 goto fail; 145 } 146 n = read(dosfs, fsinfo, fsinfosz); 147 if (n == -1 || n != fsinfosz) { 148 xperror("could not read fsinfo block"); 149 goto fail; 150 } 151 152 if (memcmp(fsinfo, "RRaA", 4) 153 || memcmp(fsinfo + 0x1e4, "rrAa", 4) 154 || fsinfo[0x1fc] 155 || fsinfo[0x1fd] 156 || fsinfo[0x1fe] != 0x55 157 || fsinfo[0x1ff] != 0xaa 158 || fsinfo[0x3fc] 159 || fsinfo[0x3fd] 160 || fsinfo[0x3fe] != 0x55 161 || fsinfo[0x3ff] != 0xaa) { 162 pwarn("Invalid signature in fsinfo block\n"); 163 if (ask(0, "fix")) { 164 memcpy(fsinfo, "RRaA", 4); 165 memcpy(fsinfo + 0x1e4, "rrAa", 4); 166 fsinfo[0x1fc] = fsinfo[0x1fd] = 0; 167 fsinfo[0x1fe] = 0x55; 168 fsinfo[0x1ff] = 0xaa; 169 fsinfo[0x3fc] = fsinfo[0x3fd] = 0; 170 fsinfo[0x3fe] = 0x55; 171 fsinfo[0x3ff] = 0xaa; 172 173 o = lseek(dosfs, boot->FSInfo * secsize, 174 SEEK_SET); 175 if (o == -1 || o != boot->FSInfo * secsize) { 176 xperror("Unable to seek FSInfo"); 177 goto fail; 178 } 179 n = write(dosfs, fsinfo, fsinfosz); 180 if (n == -1 || n != fsinfosz) { 181 xperror("Unable to write FSInfo"); 182 goto fail; 183 } 184 ret = FSBOOTMOD; 185 } else 186 boot->FSInfo = 0; 187 } 188 if (boot->FSInfo) { 189 boot->FSFree = fsinfo[0x1e8] + (fsinfo[0x1e9] << 8) 190 + (fsinfo[0x1ea] << 16) 191 + (fsinfo[0x1eb] << 24); 192 boot->FSNext = fsinfo[0x1ec] + (fsinfo[0x1ed] << 8) 193 + (fsinfo[0x1ee] << 16) 194 + (fsinfo[0x1ef] << 24); 195 } 196 197 o = lseek(dosfs, boot->Backup * secsize, SEEK_SET); 198 if (o == -1 || o != boot->Backup * secsize) { 199 xperror("could not seek backup bootblock"); 200 goto fail; 201 } 202 backup = malloc(2 * secsize); /* In case we check fsinfo. */ 203 if (backup == NULL) { 204 xperror("could not malloc backup boot block"); 205 goto fail; 206 } 207 n = read(dosfs, backup, secsize); 208 if (n == -1 || n != secsize) { 209 xperror("could not read backup bootblock"); 210 goto fail; 211 } 212 213 /* 214 * Check that the backup boot block matches the primary one. 215 * We don't check every byte, since some vendor utilities 216 * seem to overwrite the boot code when they feel like it, 217 * without changing the backup block. Specifically, we check 218 * the two-byte signature at the end, the BIOS parameter 219 * block (which starts after the 3-byte JMP and the 8-byte 220 * OEM name/version) and the filesystem information that 221 * follows the BPB (bsBPB[53] and bsExt[26] for FAT32, so we 222 * check 79 bytes). 223 */ 224 if (backup[510] != 0x55 || backup[511] != 0xaa) { 225 pfatal("Invalid signature in backup boot block: %02x%02x\n", backup[511], backup[510]); 226 } 227 if (memcmp(block + 11, backup + 11, 79)) { 228 pfatal("backup doesn't compare to primary bootblock\n"); 229 goto fail; 230 } 231 /* Check backup FSInfo? XXX */ 232 } 233 234 if (boot->FATsecs == 0) { 235 pfatal("Invalid number of FAT sectors: %u\n", boot->FATsecs); 236 goto fail; 237 } 238 239 boot->ClusterOffset = (boot->RootDirEnts * 32 + secsize - 1) 240 / secsize 241 + boot->ResSectors 242 + boot->FATs * boot->FATsecs 243 - CLUST_FIRST * boot->SecPerClust; 244 245 if (boot->Sectors) { 246 boot->HugeSectors = 0; 247 boot->NumSectors = boot->Sectors; 248 } else 249 boot->NumSectors = boot->HugeSectors; 250 251 if (boot->ClusterOffset > boot->NumSectors) { 252 pfatal("Cluster offset too large (%u clusters)\n", 253 boot->ClusterOffset); 254 goto fail; 255 } 256 boot->NumClusters = (boot->NumSectors - boot->ClusterOffset) / boot->SecPerClust; 257 258 if (boot->flags&FAT32) 259 boot->ClustMask = CLUST32_MASK; 260 else if (boot->NumClusters < (CLUST_RSRVD&CLUST12_MASK)) 261 boot->ClustMask = CLUST12_MASK; 262 else if (boot->NumClusters < (CLUST_RSRVD&CLUST16_MASK)) 263 boot->ClustMask = CLUST16_MASK; 264 else { 265 pfatal("Filesystem too big (%u clusters) for non-FAT32 partition\n", 266 boot->NumClusters); 267 goto fail; 268 } 269 270 switch (boot->ClustMask) { 271 case CLUST32_MASK: 272 boot->NumFatEntries = (boot->FATsecs * secsize) / 4; 273 break; 274 case CLUST16_MASK: 275 boot->NumFatEntries = (boot->FATsecs * secsize) / 2; 276 break; 277 default: 278 boot->NumFatEntries = (boot->FATsecs * secsize * 2) / 3; 279 break; 280 } 281 282 if (boot->NumFatEntries < boot->NumClusters) { 283 pfatal("FAT size too small, %u entries won't fit into %u sectors\n", 284 boot->NumClusters, boot->FATsecs); 285 goto fail; 286 } 287 boot->ClusterSize = boot->SecPerClust * secsize; 288 289 boot->NumFiles = 1; 290 boot->NumFree = 0; 291 292 free(backup); 293 free(block); 294 free(fsinfo); 295 return ret; 296 fail: 297 free(backup); 298 free(block); 299 free(fsinfo); 300 return FSFATAL; 301 } 302 303 int 304 writefsinfo(int dosfs, struct bootblock *boot) 305 { 306 u_char *fsinfo = NULL; 307 int secsize = lab.d_secsize, fsinfosz; 308 off_t o; 309 ssize_t n; 310 311 if ((2 * DOSBOOTBLOCKSIZE) < secsize) 312 fsinfosz = secsize; 313 else 314 fsinfosz = 2 * secsize; 315 316 fsinfo = malloc(fsinfosz); 317 if (fsinfo == NULL) { 318 xperror("could not malloc fsinfo block"); 319 goto fail; 320 } 321 322 o = lseek(dosfs, boot->FSInfo * secsize, SEEK_SET); 323 if (o == -1 || o != boot->FSInfo * secsize) { 324 xperror("could not seek fsinfo block"); 325 goto fail; 326 } 327 328 n = read(dosfs, fsinfo, fsinfosz); 329 if (n == -1 || n != fsinfosz) { 330 xperror("could not read fsinfo block"); 331 goto fail; 332 } 333 334 fsinfo[0x1e8] = (u_char)boot->FSFree; 335 fsinfo[0x1e9] = (u_char)(boot->FSFree >> 8); 336 fsinfo[0x1ea] = (u_char)(boot->FSFree >> 16); 337 fsinfo[0x1eb] = (u_char)(boot->FSFree >> 24); 338 fsinfo[0x1ec] = (u_char)boot->FSNext; 339 fsinfo[0x1ed] = (u_char)(boot->FSNext >> 8); 340 fsinfo[0x1ee] = (u_char)(boot->FSNext >> 16); 341 fsinfo[0x1ef] = (u_char)(boot->FSNext >> 24); 342 343 o = lseek(dosfs, o, SEEK_SET); 344 if (o == -1 || o != boot->FSInfo * boot->BytesPerSec) { 345 xperror("Unable to seek FSInfo"); 346 goto fail; 347 } 348 n = write(dosfs, fsinfo, fsinfosz); 349 if (n == -1 || n != fsinfosz) { 350 xperror("Unable to write FSInfo"); 351 goto fail; 352 } 353 354 free(fsinfo); 355 356 /* 357 * Technically, we should return FSBOOTMOD here. 358 * 359 * However, since Win95 OSR2 (the first M$ OS that has 360 * support for FAT32) doesn't maintain the FSINFO block 361 * correctly, it has to be fixed pretty often. 362 * 363 * Therefore, we handle the FSINFO block only informally, 364 * fixing it if necessary, but otherwise ignoring the 365 * fact that it was incorrect. 366 */ 367 return 0; 368 fail: 369 free(fsinfo); 370 return FSFATAL; 371 } 372